This invention relates to tufting machines and more particularly to a new and improved patterning device for shifting the needles laterally across the tufting machine.
The art of tufting incorporates a plurality of yarn carrying spaced needles extending transversely across the machine and reciprocated cyclically to penetrate and insert pile into a backing fabric fed longitudinally beneath the needles. During each penetration of the backing fabric a row of pile is produced transversely across the backing. Successive penetrations result in a longitudinal row of pile produced by each needle. This basic method of tufting limits the aesthetic appearance of tufted carpet so produced.
Methods have been devised which effect relative shifting between the needles and the backing fabric which provide patterning capabilities and which break-up the noticeable alignment of the longitudinal rows that detract from the appearance of a carpet. Moreover, when using yarns of different color in different needles the shifting selectively transfers yarns of one color into a row normally having a different color. For example, U.S. Pat. of Bryant et.al. No. 3,026,830, Mar. 27, 1962 discloses a sliding needle bar mechanism so as to shift the needle bar laterally as it is reciprocated so that the needles on successive penetrations selectively cooperate with different individual loopers.
In this known shifting arrangement lateral movement of the needles relative to the backing fabric is controlled by a pattern cam similar to that illustrated in the aforesaid patent. Due to the physical limitations of cams the maximum amount of information that can be cut into a cam limits the available patterns produced. Thus, since there is a longitudinal pattern repeat every revolution of the pattern cam, the pattering capabilities of the prior art shifting devices are limited. The cams presently used to effect program shift are approximately one foot in diameter. To increase the pattern repeat interval would require that the cams be of greater diameter. However, the diameter and physical size of the cams are limited due to practical considerations. Moreover, the physical limitations of the cams and the difficulty in cutting intricate cams do not permit carpet designers the desired flexibility of pattern selection. Furthermore, another disadvantage of using pattern cams is that whenever a pattern is changed a different pattern cam must be installed. The time for changing cams together with the maintenance of the inventory of pre-cut pattern cams which must be on hand is an obvious disadvantage.